1. Field of the Invention
This invention relates, in general, to article inspection apparatus and, more specifically, to article inspection apparatus which converts the radiation pattern of an article or object into a visible light image.
2. Description of the Prior Art
Radiation, particularly x-rays, is used in many different fields to inspect articles, such as manufactured parts, packages, etc. for defects, surface cracks, internal foreign objects, etc., as well as in medical diagnostic procedures for examining patients. In such inspection or diagnostic apparatus, radiation from a suitable source is directed at and penetrates the article or patient. The radiation, some of which is absorbed by the article, is then received by the screen of a conventional camera which produces a light image corresponding to the radiation pattern of the object. Such exemplary inspection systems are shown in U.S. Pat. Nos. 4,193,089 and 4,473,843.
It is also known to direct the radiation through an object onto a stimulatable phosphor screen which records the radiation image and which can be read out by use of stimulating rays directed onto the screen.
In all such cases, it has been found that light images produced on the camera screen or on the stimulatable phosphor screen are relatively low in intensity thereby making it difficult to obtain a clear and easily viewable image of the object. Such clearness is essential in inspecting the surface of manufactured parts for minute defects, such as surface cracks, which can only be a few millionths of an inch in width or length.
To overcome these problems, it is conventional to employ an x-ray detector and light intensifier between the object and the camera as shown in U.S. Pat. No. 4,473,843. Such an image intensifier includes a series of lenses and electronic circuits which amplify the image impinging upon the screen at one end of the intensifier and display the amplified image at a screen at a second end which can be detected by the camera. However, while such image intensifiers are effective at improving the x-ray produced image, such image intensifiers are expensive and relatively long in length thereby increasing the overall size of inspection apparatus and adding to its total cost. Such intensifiers are also subject to scintillation noise which causes distortion of the viewed image.
Thus, it would be desirable to provide a radiation image inspection apparatus which overcomes the problems of previously devised radiation inspection appartus. It would also be desirable to provide a radiation image inspection apparatus which eliminates the need for a conventional image intensifier. Finally, it would be desirable to provide a radiation image inspection apparatus which is small in size, has a relatively low manufacturing cost and is capable of producing clear images with a resolution of a few millionths of an inch.